Apart from the fact that MetaMask is an altcoin wallet not a "shield"; technically you should keep your bitcoin offline so that getting your online system infected wouldn't affect them. And if you want protection install uBlock Origin and a decent Anti Virus on your system that has net protection.
I know a lot of people here dislike Ethereum, MetaMask does have a feature of
potentially showing a warning if the user opens a phishing site, which I don't think uBlock Origin has that feature.
There's this one plugin that's made exclusively for blocking phishing sites though, so it should be a better pick than MetaMask. I forgot the name of the plugin.
Most browsers already have built in phishing protection. uBlock Origin offers additional protection. The default lists are already good enough for most people but if someone really wants to use Metamask's domain filter it can be imported into uBO by going into the dashboard and pasting the URL to the hosts.txt file from their GitHub.